Wednesday, 2 May 2012

Wind farms linked to climate change

Wind
farms can cause climate change, according to new research, that shows for the
first time the new technology is already pushing up temperatures.

Usually
at night the air closer to the ground becomes colder when the sun goes down and
the earth cools. But on wind farms the motion of the turbines mixes the warmer
air higher in the atmosphere with the ground-level air, pushing up the overall
temperature.

Satellite
data over a large area in Texas, covered by four of the world's largest wind
farms, found that over a decade the local temperature went up by almost 1°C as
more turbines were built. This could have long-term effects on wildlife living
in the vicinity of larger wind farms. It could also affect regional weather patterns
as warmer areas affect the formation of cloud and even wind speeds. And, as
even bigger wind farms are built around the world, there are calls for further
research into whether it is likely to affect climate change on a larger scale.

Texas
is the largest producer of wind power in the US. It is reported that China is
erecting 36 wind turbines every day. Liming Zhou, Research Associate Professor
at the Department of Atmospheric and Environmental Sciences at the University
of New York, who led the study, said further research was now needed into the
effect of the new technology on the wider environment. "Wind energy is
among the world's fastest growing sources of energy. The US wind industry has
experienced a remarkably rapid expansion of capacity in recent years,"
While converting wind's kinetic energy into electricity, wind turbines modify
surface atmosphere exchanges and transfer, of energy, momentum, mass
and moisture within the atmosphere. These changes, if spatially large enough,
might have-noticeable impacts on local to regional weather and
climate."

The
study, published in the scientific journal Nature, found a warming trend of up
to 0.72°C per decade as more turbines were built. The team studied satellite
data showing land surface temperature in west-central Texas: The study
said: "Despite debates regarding the possible impacts of wind farms on
regional to global scale weather and climate, modelling studies agree that they
can significantly affect local scale meteorology."

"Our
results show a significant warming trend of up to 0.72°C per decade,
particularly at night-time, over wind farms relative to nearby non-wind farm
regions. We
attribute this warming primarily to wind farms as its spatial pattern and
magnitude couples very well with the geographic distribution of wind farms. The
spatial pattern of the warming resembles the geographic distribution of wind
turbines and the year-to-year land surface temperature over wind farms shows a persistent upward trend from 2003 to 2011, consistent with the increasing number of operational wind
turbines with time," said Prof Zhou. However he pointed out that the most
extreme changes were at night and the overall, changes may be smaller. In
addition, they weremuch smaller than the estimated change caused by other
factors such as man made global warming. "Overall, the warming effect
reported in this study is local and is small compared to the strong background
year-to-year land surface temperature changes," he added.

Prof Steven Sherwood, co-director of the Climate
Change Research Centre at the University of New South Wales in Australia, the
research was "pretty solid". "This makes sense, since at night
the ground becomes, much cooler than the air just a few hundred meters above
the surface,, and the wind farms generate gentle turbulence near the ground
that causes these to mix together, thus the ground doesn't get quite as
cool."